Abstract/Project summary: Protein quality control (PQC) mechanisms are required for cellular health, to prevent age-related diseases and to avoid premature aging and senescence. PQC substrates are recognized by specialized components and are typically degraded by the ubiquitin proteasome system (UPS). To explore the relationship between PQC and age-related disease, the applicant?s lab identified a novel substrate for this pathway, mutant Triosephosphate Isomerase (TPI). Numerous subtle amino acid substitutions in TPI are pathogenic, and result in progressive multisystem disease. Importantly, the mutant protein retains function and it is now known that increased turnover of the functioning protein by the UPS underlies disease pathogenesis. Because the molecular and physical basis of PQC substrate recognition is poorly understood, especially for soluble cytosolic proteins such as mutant TPI, a genome-wide genetic screen was performed that led to the identification of numerous novel regulators of mutant TPI turnover. The immediate goal of the screen is to define how mutant TPI is pathologically selected for disposal by the UPS and to identify pharmacologic targets for a therapy. The screen identified all of the known and predicted regulators of TPI (HSP70, HSP90, proteasome subunits, ligases, etcetera) as well as many additional modifiers of turnover. Importantly, several of these regulators are highly conserved proteins of currently ?unknown? function. We propose here to rigorously validate these regulators of mutant TPI and extend our analysis of the novel regulators by examining their role in the turnover of panel of other biomedically relevant substrates including alpha-synuclein, estrogen receptor and cystic fibrosis transmembrane conductance regulator. Overall this project will identify and validate conserved human PQC proteins that are critical to healthy animal aging and therapeutic targets for various progressive disease states.